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Mosquito In Martinsville Test Positive For West Nile Virus

Last updated on Friday, July 27, 2012

(MARTINSVILLE) - Morgan County Health Department officials reported Monday that a mosquito pool in the Martinsville area recently tested positive for the West Nile virus, the first sign of the potentially deadly virus in Morgan County this year.

But even though Monroe, Owen, Greene, Lawrence and Brown counties are not among the 14 Indiana counties in which West Nile virus-infected mosquitoes have been found this year, it does not mean the virus is not lurking in their local mosquito populations. The virus was been found in a mosquito in Orange County in June.

"Even though no West Nile positive mosquitoes have been found here, we can safely assume the West Nile virus is in Monroe County and every other county in the state," said environmental health specialist Simeon Baker, who manages Monroe County's mosquito surveillance program. "We don't want people to get a false sense of security."

Baker said this year's hot, dry summer has accelerated the breeding cycle of mosquitoes, and caused bodies of water to shrink and become stagnant, forming the perfect breeding environment for the Culex mosquito -- which is more likely than other mosquitoes to carry the West Nile virus.

"When you have heavy rains and a lot of floodwater, you get more mosquitoes, but most of them are not the Culex mosquito," he said. "The Culex loves to breed in small containers and stagnant bodies of water that are rich in organic material."

Testing

Every spring and summer, employees from the Indiana State Department of Health set up mosquito traps throughout every county in the state. The traps are baited with a fermenting hay mixture that attracts adult mosquitoes seeking to lay their eggs.

But as the blood-sucking insects approach the hay, a fan blows them into some fine netting. Samples of 100 or so mosquitoes, called "pools," are then tested for West Nile in the health department's lab.

No West Nile virus-infected mosquitoes were found in Monroe County for several years, until they were discovered in 2008. They were found again in 2010, but not 2009.
If the state does find West Nile-infected mosquitoes in Monroe County, Baker will not reveal the site or sites where the mosquitoes were found, because he would not want people to either panic or feel they are safe.

"Mosquitoes are constantly migrating and can fly up to a mile for a blood meal," he said.

Human cases

So far this year, there have been no reported human cases of West Nile virus in Indiana.
In 2002, the year in which the state's first human case of West Nile virus was reported, there were 293 human cases of West Nile, and 11 fatalities.

From 2002 through 2009, there are have been 645 cases of human West Nile, and 31 fatalities. Last year there were 9 human cases in the state, resulting in one death, and in 2010 there were 13 human cases and one death.

Prevention

Mosquitoes that carry the West Nile virus breed in places such as ditches, open septic systems, discarded tires, birdbaths, wading pools, untended swimming pools and swimming pool covers, clogged roof gutters and any unused containers that hold water for several days at a time.

"Even a small bucket that has stagnant water in it for seven days can become home to up to a thousand mosquitoes," Baker said.

Baker said people can protect themselves from being bitten by limiting outdoor activity between dusk and dawn, when mosquitoes are most likely to bite; using an insect repellent containing DEET; wearing shoes, socks, long pants and a long-sleeved shirt when outdoors; wearing clothes that are light-colored and made of tightly woven materials; making sure that all windows and doors have screens; and using mosquito netting when sleeping outdoors.

Infecting Humans

The West Nile virus is transmitted to a human by a mosquito that has first bitten an infected bird. A person who is bitten by an infected mosquito may show symptoms 3 to 15 days after the bite.

Most people who get infected will have no symptoms or mild symptoms -- such as a fever, headache, body aches, swollen lymph glands or a rash.

But anyone who develops symptoms such as high fever, neck stiffness, nausea, vomiting, sore joints, confusion, muscle weakness or severe headaches should see a health care provider immediately for diagnosis and treatment.

There is no standard treatment for West Nile virus, and no vaccine is available for humans.

In about 1 percent of West Nile cases, the infected person -- especially children and those older than 50 -- will develop a more severe form of the disease, such as encephalitis (inflammation of the brain) or meningitis (inflammation of the tissues that cover the brain and spinal cord). Both conditions can be fatal.
More information is available at www.in.gov/isdh.

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